1. Field of the Disclosure
The present disclosure of invention relates to a method of forming a metal pattern on a display substrate and a method of manufacturing a display substrate including the metal pattern. More particularly, example embodiments in accordance with the present disclosure of invention relate to a method of forming a metal pattern for improving an etching margin and a method of manufacturing a display substrate including such margin tolerant metal pattern.
2. Description of Related Technology
Generally, a display substrate used for display devices such as Liquid Crystal Displays (LCD's) includes a plurality of thin-film transistors (“TFT”) integrally formed on the substrate as switching elements for driving respective pixel regions. The display substrate also typically includes one or more signal lines connected to each of the TFTs and pixel electrodes that are selectively charged and discharged according to data and gate signals supplied over the signal lines. More specifically, the signal lines may include a gate line that is provided for transmitting a gate driving signal to a gate electrode of a respective TFT, and a data line that extends to cross with the gate line and to transmit a data driving signal to a source electrode of a respective TFT.
As a size of the display device is increased and as desires by customers for higher resolutions (e.g., more pixels per unit length in the gate line longitudinal direction) increase, relative lengths of the gate lines and/or of the data lines tend to increase while comparative widths (relative to lower resolution panels) of the gate lines and/or the data lines tend to decrease. As a result, electric resistances of such signal lines disadvantageously tend to increase. Also as a result, corresponding signal conveying time constants, or resistance-capacitance factors (“RC” factors) of the signal lines disadvantageously tend to increase where increased RC factors lead to increased signal delays and slower display response times. One answer to the problem has been to use relatively low resistance, but also relatively difficult to etch and thus expensive metals for forming the gate lines and/or the data lines where the relatively low resistivities of such metals help to solve the RC signal delay problem.
More specifically, copper (Cu) is sometimes used as the metal having a relatively low resistivity for forming the gate lines or the data lines. On one hand, copper has excellent electric conductivity and is abundantly available as a natural resource; albeit sometimes at higher costs than competing other metals. In addition, copper has a resistance much lower than aluminum or chrome (examples of competing other metals). On the other hand, when it comes to lithographically patterning a metal layer, the resistance of copper to being etched by a respective oxidizing agent is higher than that of aluminum or chrome so that a strong oxidizing agent and/or longer etch times are required for etching a copper-based layer of equal thickness during lithographic patterning of a metal layer containing copper.
Although there is available a copper etchant including the strong oxidizing agent for effectively etching the copper-based layer, patterns of other materials which have already been formed and patterned on the substrate before the patterning of the copper-based layer may be easily damaged in the etching of the copper-based layer by the strong oxidizing agent. Also, when the copper etchant includes the strong oxidizing agent by itself, an etch rate of the copper-based layer is hard to control and in the attempt to save underlying and pre-patterned layers, the copper-based layer may be under-etched. Thus, the copper-based layer may be etched to have a shape different from the shape which is theoretically called for by the circuit design and display performance may suffer.
It is to be understood that this background of the technology section is intended to provide useful background for understanding the here disclosed technology and as such, the technology background section may include ideas, concepts or recognitions (e.g., that of a moderated version of the strong oxidizing agent) that were not part of what was known or appreciated by those skilled in the pertinent art prior to corresponding invention dates of subject matter disclosed herein.